Dynamic Stability Analysis of Cages in High-Speed Oil-Lubricated Angular Contact Ball Bearings

To investigate the cage stability of high-speed oil-lubricated angular contact ball bearings, a dynamic model of cages is developed on the basis of Gupta’s and Meeks’ work. The model can simulate the cage motion under oil lubrication with all six degrees of freedom. Particularly, the model introduces oil-film damping and hysteresis damping, and deals with the collision contact as imperfect elastic contact. In addition, the effects of inner ring rotational speed, the ratio of pocket clearance to guiding clearance and applied load on the cage stability are investigated by simulating the cage motion with the model. The results can provide a theoretical basis for the design of ball bearing parameters.     

影响排球比赛发球的因素及调整对策

从心理学角度入手,分析研究运动员在排球比赛中临场的心理状态、自我调节及心理训练方法,对其提出正确的心理定位和建议对策。     

文化视野下的我国三大球发展困境及其出路

在文化视角下对我国三大球的发展困境及其出路进行了回眸与反思。提出文化视野下我国三大球的发展困境主要体现在,精神文化层面：“金牌战略”的核心价值理念错误引导、我国传统文化思想的束缚、三大球文化创新意识和能力缺乏;制度文化层面：举国体制的时效性下降、人才培养模式单一、行政管理体制存在弊端;物质文化层面：三大球联赛职业化水平低、专业队伍建设及后备人才匮乏、教练员数量和质量限制。三大球的发展出路体现在精神文化层面培养政府和民众的三大球精神文化自觉意识;制度文化层面通过制度创新激活三大球自主创新的活力;物质文化层面推进三大球的市场化、职业化与产业化进程,凝聚复兴的物质力量。     

Acute effects of different warm-up protocols on highly skilled golfers’ drive performance

Previous research has highlighted the positive effect that different warm-up protocols have on golf performance (e.g. Sorbie et al., 2016; Tilley & Macfarlane, 2012) with the design of warm-ups and programmes targeting and improving golf performance through the activation and development of specific muscle groups. This study aimed to examine the acute effects of two warm-up protocols on golf drive performance in comparison to a control condition. Using a randomised counterbalanced design over three testing sessions, twenty-three highly skilled golfers completed the control, dynamic and resistance-band warm-up conditions. Following each condition, a GC2 launch monitor was used to record ball velocity and other launch parameters of ten shots hit with the participants’ own driver. A repeated-measures ANOVA found significant increases in ball velocity (η_p² = .217) between the control and both the dynamic and resistance-band warm-up conditions but no difference between these latter two, and a reduction in launch angle between control and dynamic conditions. The use of either a dynamic stretching or resistance-band warm-up can have acute benefits on ball velocity but golfers should liaise with a PGA Professional golf coach to effectively integrate this into their golf driving performance.     

平衡训练影响踝关节功能稳定性的研究

目的:对踝关节不稳人群进行不同方式的平衡训练,以提高踝关节平衡控制能力及稳定性,减少踝关节损伤的发生几率;比较不同平衡训练方法对改善踝关节稳定性的实用性及优劣性。方法:进行为期3周的Biodex Balance System仪器及Bosu平衡球训练,测试踝关节稳定性。结果及结论:结果显示,Biodex Balance System仪器和Bosu平衡球都能显著提高个体踝关节稳定性及方向控制能力;Biodex Balance System仪对踝关节稳定性的提高更为明显。     

Small Nation,Big Sport: Basque Ball – Its Past and Present Cultural Meanings for the Basques

Abstract

The Basques are a nation living in the Basque Country – a territory that is divided between two states – France and Spain. Isolated in the mountainous terrain they have preserved their original culture and collective identity. However, they still need to struggle for recognition, using some elements of their own culture to promote their identity and reject their status as a peripheral region of Spain or France. One of such elements is sport, especially so-called ‘traditional sports’ which this nation has preserved over centuries. The aim of this paper is thus to analyze one example of such a sport – Basque ball and its historical and present situation, connections with other elements of culture and its socio-cultural importance for the Basques.     

不同类型运动技能保持特征的比较研究

以某大学普通专业107名学生为被试,考察不同类型运动技能的保持特征,并比较其差异。实验设计不同组织水平的武术套路项目(n=62)和皮艇球项目(n=45)。每组被试在完成9周36学时的技能学习任务后进行评分。随后随机分为5个小组,将1~5小组被试随机分配到1,2,6,15,31天的复测中,收集相应时间点的技能保持量,最后绘出保持率曲线。实验研究的结果表明:随着时间间隔的增加,不同组织水平动作技能的保持特征有所不同,并对这些差异存在的可能原因进行理论分析。     

普通高校太极柔力球选项课教学内容及教学方法的研究

“要将新兴运动项目引进学校体育课堂”,这是对高校体育教学提出的更深更广的要求．太极柔力球是一项具有鲜明民族特色的新兴体育运动项目,是以弧形引化过程触球并顺势将球抛出为主要技术特征的持拍球类运动,融健身、娱乐,观赏、竞技于一身,具有较高的健身价值．本文就普通高校体育开设太极柔力球选项课的教学内容及教学方法等方面进行论述,旨在为这一新兴运动项目的进一步推广提供教学参考。     

亚洲国家集体球类项目竞技实力的比较研究

运用文献法、数理统计法、比较分析法对亚洲各个国家或地区在第26、27、28届夏季奥运会集体球类项目上的竞技实力进行了比较研究,研究结果:亚洲各个国家或地区可以分成两大集团,第一集团包括中国、韩国、日本,第二集团包括中国台北、巴基斯坦、印度、伊拉克,集团之间的实力差距悬殊;在男子项目上,韩国、日本的实力高于其它国家或地区,女子项目的实力强弱顺序依次是中国、韩国、日本与中国台北;在各个项目上,竞技实力的强弱呈现出完全不同的变化,各个国家或地区都具有相对优势项目,但都不具备集团优势。     

论木球与高尔夫

从术球与高尔夫的起源、技术特征、运动特点、心理特点等方面进行比较分析,旨在为术球在国内乃至世界各地进一步推广和发辰提供参考。